Definitely do your research, not just on the chiropractor
but on chiropractic itself and whether it's
the best thing for what ails you (as opposed to, say, physiotherapy). If their website and/or promotion materials don't make it clear, ask any prospective chiropractor
where they stand on subluxation theory and whether it is the cause of most (if not all) diseases. It seems that chiropractors fall into two camps,
"straights" and "mixers". The former camp treats spinal manipulation as a cure-all while the latter is more open to physiotherapy and other aspects of mainstream medicine. Approach anyone from the "straights" camp with caution as the belief spinal manipulation cures all ills has led some chiropractors to claim they can cure ailments such as
ADHD, autism, and cancer.
You might also want to inquire as to any
chiropractor's stance on vaccines, especially if you have young children, elderly, or immunocompromised people in your life. The world of chiropractic seems to be a hotbed for all manner of pseudoscience,
especially anti-vaccine beliefs, which have been a feature of the practice almost
as long as the practice has existed. Keep an ear out for phrases such as "pro-safe vaccines" or "pro-informed choice" as they're euphemistic fig leaves for the same position.